A new treatment could prevent delayed asthma attacks, which can occur several hours after exposure to allergens, a study showed today.
Research led by scientists from Imperial College London could explain why around half of people with asthma experience a “late phase” of symptoms.
Scientists found that blocking sensory nerve functions stopped a “late asthmatic response” in mice and rats.
The findings, published in the journal Thorax, could lead to better treatments for the disease, researchers said.
An estimated 300 million people suffer from asthma. Symptoms are commonly triggered by allergens in the environment, such as pollen and dust mites, and these stimuli can cause the airways to tighten within minutes, causing breathing difficulties.
Many sufferers also experience a “late asthmatic response” three to eight hours after exposure to allergens, causing breathing difficulties which can last up to 24 hours.
When sufferers have an “early response”, the allergen is recognised by mast cells, which release chemical signals that cause the airways to narrow.
The mechanism behind the late phase has remained unclear but, in new research on mice and rats, scientists found evidence that the late asthmatic response happens because the allergen triggers sensory nerves in the airways.
These nerves activate reflexes which trigger other nerves that release the neurotransmitter acetylcholine, which causes the airways to narrow.
Scientists claim that if the findings translate to humans, it would mean that drugs which block acetylcholine – called anticholinergics – could be used to treat asthma patients who experience late phase responses.
At present steroids are the main treatments prescribed for asthma, but they are not effective for all patients.
A recent clinical trial involving 210 asthma patients found that the anticholinergic drug tiotropium improved symptoms when added to a steroid inhaler, but the reason for this was unexplained.
Professor Maria Belvisi, from the National Heart and Lung Institute at Imperial College London, who led the research, said: “Many asthmatics have symptoms at night after exposure to allergens during the day, but until now we haven’t understood how this late response is brought about.
“Our study in animals suggests that anticholinergic drugs might help to alleviate these symptoms, and this is supported by the recent clinical data.
“We are seeking funding to see if these findings are reproduced in proof of concept clinical studies in asthmatics.”
Professor Stephen Holgate, funding board chair for the Medical Research Council, which funded the study, said: “Unravelling the complex biology of asthma is vitally important, as it is an extremely dangerous condition which exerts lifelong damaging effects.
“The Medical Research Council is committed to research that opens doors to improving disease resilience, particularly in conditions which attack our body over the long term.
“Studies like this are making really important progress and, whilst we must always be cautious when taking findings from rodents into humans, these are very interesting and potentially important results.”
Dr Samantha Walker, director of research and policy at Asthma UK, said: “This research seeks to understand the causes of chronic asthma symptoms and may pave the way for identifying new treatments for people with asthma in the future.”